The present invention relates to pump systems having variable-pressure shaft seals and other mechanisms to protect components from moisture-related damage.
Pump systems often include various components and structures designed to protect the bearing frame or other portions of the pump system from pumped liquid or other moisture. For example, many types of pump systems employ various seals in connection with rotating shafts. Such a shaft might be used to drive a pump impeller, to provide rotational output from a motor, or for other purposes. The shaft extends through various openings in the pump system (e.g., through the bearing frame), and these openings are often sealed in order to provide a waterproof barrier or enclosure. In a centrifugal pump, for example, the pump casing typically is sealed at the opening where the impeller shaft enters the casing, in order to prevent pumped liquid from leaking out through the opening along the impeller shaft. Such leakage can potentially cause damage to bearing assemblies, to the motor, or to other components of the pump system, or can cause an environmental hazard. In addition to the shaft seals described above, various other structures and methods may be used to provide protection, including waterproof casings, non-shaft seals, sealed enclosures, etc.
Improving the performance of seals and increasing other protections against water damage are important goals in the design of bearing frames and other pump system components. Depending on the pumping application and/or pumping conditions, the protection afforded by many existing pump systems often is limited or inadequate. Many existing systems are ill-equipped to protect against the risk of flooding, which can lead to damage to bearing assemblies, motors or other components. Existing shaft seals, for example, often are designed to protect against only splashing or brief immersions in liquid. Many pump system components are provided with no protection at all against the risk of flooding.
Accordingly, an improved pump system is provided, including an impeller and an impeller shaft, which has one end secured to the impeller and another end configured to coupled to a motor in order to drive the impeller. The pump system further includes a substantially liquid-proof barrier which has an opening through which the impeller shaft extends. The opening in the barrier is sealed with a shaft sealing system that includes a supply chamber fluidly coupled with a cavity. The cavity surrounds, and is at least partially bounded by, the impeller shaft. The shaft sealing system further includes a pressure mechanism that is configured to pressurize lubrication matter contained within the supply chamber and cavity, so as to inhibit liquid from passing along the impeller shaft through the cavity and thereby penetrating the liquid-proof barrier. The pressure mechanism is further configured to vary pressure of the lubrication matter based on atmospheric pressure surrounding the pump system.
The pump system may further include a bearing frame through which the impeller shaft extends. In such a case, the shaft sealing system (or more than one such system) may be employed to seal the bearing frame and thereby inhibit penetration of moisture into the bearing frame. In addition to or instead of the shaft sealing system(s), the bearing frame may be provided with a vent that is closeable via operation of a float valve assembly upon flooding of the pump system.